The disk drive industry is extremely competitive and therefore, disk drive demand tends to be characterized by a high sensitivity to price per unit storage capacity. To achieve high data storage capacities within a particular disk drive package, multiple disk platters are typically mounted concentrically to a spindle motor and operated in conjunction with a set of ganged heads, each of which is supported on a gimbal structure which forms a part of a suspension member (hereinafter, "suspension").
The suspensions, in turn, are mounted to rigid actuator arms which are connected to a common, rotatable structure typically known as an E-block. The E-block is attached to a voice coil motor structure to form a mass-balanced, closed-loop servo positioning, rotary actuator structure capable of selectively positioning the ganged heads at various radial locations or tracks relative to the disks. Since the suspensions form a part of the mechanical structure within the servo loop, the dynamic characteristics of the suspensions can limit the achievable servo system performance.
Copending U.S. application Ser. No. 08/249,525 entitled METHOD FOR CHARACTERIZING AND CONTROLLING IN-PLANE STIFFNESS OF LOAD BEAM WITHIN HEAD-GIMBAL ASSEMBLY OF A HARD DISK DRIVE, now U.S. Pat. No. 5,471,734, the disclosure of which is hereby incorporated by reference, teaches that the spring and loadbeam of a suspension can be geometrically configured such that the first torsional resonance mode has a minimum or optimum sensitivity of gain with respect to handling and manufacturing tolerances. Specifically, the sensitivity of the first torsion gain can be reduced by controlling the Z-axis height of the end of load beam region adjacent to the spring. By thus reducing the sensitivity of the gain to manufacturing processes, the manufacturing yields of load beam fabrication and headstack assembly operations, for example, can be dramatically improved. This reduced gain sensitivity does not imply that the magnitude of the gain itself is reduced, however, thus such suspensions may not show improved absolute performance, notwithstanding the improvement in the consistency of the performance.
Thus a hitherto unresolved need exists for a suspension which exhibits reduced first torsional gain sensitivity to manufacturing processes while concurrently providing a reduced nominal magnitude of gain to facilitate improved servo system performance.